Problem: Solve for $x$ : $x - 18 = 24$
Explanation: Add $18$ to both sides: $ \begin{eqnarray} \\ x - 18 &=& 24 \\ \\ {+18} && {+18} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-18 + x} &\hphantom{=}& \hphantom{24} \\ x &=& 24 {+ 18} \\ \end{eqnarray} $ Simplify. $ x = 42$